Gyroscope



P. F. HAYNER Dec. 1, 1959 GYROSCOPE Original Filed Nov. 13. 1953Aftorney inertial guidance instrument.

United States Patent Ofilice Re. 24,741 Reissued Dec. 1, 1959 GYROSCOPEPaul F. Hayner, Nashua, N.H., assignor, by mesne assignments, to SandersAssociates, Incorporated, Nashua, N.H., a corporation of DelawareOriginal No. 2,839,932, dated June 24, 1958, Serial No. 391,981,November 13, 1953. Application for reissue September 30, 1958, SerialNo. 764,467

Claims. (CI. 74-55) Matter enclosed in heavy brackets appears in theoriginal patent but forms no part of this reissue specification; matterprinted in italics indicates the additions made by reissue.

This invention relates generally to [gyroscopes] inertial guidanceinstruments and, more particularly, to gyroscopes of the type employedin modern aircraft, guided missiles and the like. It is particularlydirected to the provision of a gyroscope which is of exceedingly smallsize while, at the same time, having an improved performance relative tosimilar instruments of larger size.

This is a re-issue of US. Patent 2,839,932, issued June 24, 1958.

In reducing the size of the gyroscope, while improving its performance,consideration must be given to various factors including the: gyrogimbal construction and its mounting system. Moreover, in all gyroscopesof this type, it is highly desirable if not essential that their gimbalsbe as free as possible from the influence of tem perature changes ontheir relatively movable parts.

It is, therefore, an object of the present invention to provide animproved [gyroscope] inertial guidance instru ment capable ofcompensating for variations in damping fluid viscosity due totemperature variations.

More specifically, it is an object of the invention to provide animproved gyroscope with means for minimizing effects of temperaturevariations upon its movable parts.

Other and further objects will become apparent from the followingdescription.

In accordance with the invention, there is provided an The instrumentincludes a mass member and a housing for the mass member pivotallysupporting it for motion about an axis. A viscous fluid within thehousing surrounds the member for damp ing its motion. An expansible,annular member is dis posed between the mass member and the housing fordecreasing the space between the plastic member and the housing withincreases in temperature, thereby minimizing the effects of variationsin the viscosity of the fluid.

In accordance with the embodiment in the present invention, there isprovided a gimbal for the gyro rotor with a housing for the gimbalpivotally supporting it and permitting its movement about an axisperpendicular to the rotors axis of spin. A fiuid or viscous liquid,such as oil, is carried within the housing surrounding the gimbal fordamping its movement. An annular member, secured to the gimbal, expandswith increases in temperature so as to decrease the space between thegimbal and the housing. The changes in the size of the annular membereffect a compensation for the variation in the damping factor of thefluid.

For a more detailed description of the present invention, reference maynow be made to the following description taken in connection with theaccompanying draw- In the drawing, Fig. l is a perspective side view ofgyroscope embodying the present invention shown in actual size; Fig. 2is an enlarged, side elevation view, partly in section, of the gyroscopeof the present inven 2 tion; and Fig. 3 is an exploded, perspectiveView, partly in section, of the gyro shown in Figs. 1 and 2.

Referring now to the drawing, and particularly to Figs. 2 and 3, thegyro of the present invention is shown com prising a housing or casing 1of generally cylindrical form having attached at one end, a cap 2 whichmay be mounted in a suitable place.

Provided in the end cap 2 are adjusting screws 3 and leads 4. Anadjusting ring 5 is provided adjacent to the end cap 2 with rivet holes6 and pick-off adjustment elements 7, as shown. An adjusting sealer 8 isdisposed at the opposite side of ring 5, followed by the pick-off windings 9, in which there is disposed a pick-01f stator 10 and rotor 11, asshown.

The gimbal 12 is disposed, in a central position in the housing as shownin Fig. 2, and comprises the split upper and lower sections 129. and 12bwhich are shown in detail in Fig. 3.

Torsion bars 13 are provided at opposite ends of the gimbal. These barsare preferably of an integral, elastic metal construction, in thepresent embodimnet, beryllium copper. They comprise a narrow centralportion which provides the spring restraint, that is, it is capable ofan axial twisting movement and enlarged end portions which areintegrally formed as a part of the torsion bars for effecting a rigid,strong, and secure support.

Also, for this purpose the enlarged end portions are tapered and thesupports in the gimbal in the end cap 2, and the hub or mount 27, of theS-spring assembly, presently to be described, are correspondinglytapered. There is thereby provided rigid and secure supports whichpermit the rotative movement of the gimbal about the output axis, causedby the angular velocity of the rotor. The torsion bars also provide arestraining torque which resists this angular movement about the outputaxis and returns the gimbal and rotor to their normal relative angularpositions immediately after the input force of the gyro has beenremoved. Friction is thus essentially eliminated from the output axis ofthe gyro.

By virtue of these torsion bars no moving bearings are required for thegimbal suspension and both support and centering of the gimbal areaccomplished.

The nuts 15 at the top and bottom of the gimbal sections secure theshaft 16 to the rotor 17. The gyro rotor 17 is preferably constructed ofa high density material such as tantalum. Suitable retainers andbearings are provided at each end of the rotor shaft. Caps 18 areprovided for the rotor at each end thereof. The two sections of thegimbal are retained by the ring 21 and the pickoff rotor 11, as shown.

An annular temperature compensator member of damper cylinder 22, inwhich several balance screws may be secured, is secured at one end ofthe gimbal 12. It is this member and its associated parts that comprisefeatures to which the present invention is particularly directed andtheir function will now be referred to in more detail.

The damping member or cylinder 22 is shaped as shown in the drawing,particularly Fig. 3. It is constructed of a suitable material such asnylon which expands with in creasing temperature. This reduces the gapbetween the member 22 and the housing. The housing is filled with fluid,preferably oil, of the kind commercially available and known as DowCorning 200 Series Silicone.

The dominant resonance of the gyro (output axis inertiatorsion spring)is damped by the viscous forces from shearing action on the fluid whichfills the gap between the gyro case 1 and the member 22.

The usual nominal value of damping provided isin the vicinity of 0.5 to0.7 critical. A fair latitude of choice is available through the useoffluids of slightly different viscosity,

To facilitate the elimination of heaters and temperature control formany applications, inherent variation of damp ing with temperature isminimized. Viscosity of the Dow Corning 200 Series Silicone fluids, onlydoubles for each 50 F. decrease of temperature, the lowest coetficientavailable in damping fluids. v

The member 22 more particularly serves to minimize variations of thedamping factor of the fluid in the upper half of the temperatureoperating range, through a compensating variation of the size of theclearance gap be tween this member and the case 1. This is accomplishedby virtue of the differential expansions between the member 22 and themetal case. As the temperature is raised, a point is reached at whichthe member 22 rubs and finally seizes on the housing 1 and locks thegimbal 12 in position. This action sets an upper operating temperaturelimit, for the gyro, though it causes no damage and the gyro can surviveappreciably higher temperatures. When the temperature is again broughtdown within the operating range, the damper member shrinks, releasingthe gimbal and normal operation is resumed.

Also, for the purpose of preventing special strain on the torsion barsby different rates of expansion of the parts within the gyro, withtemperature changes, there is provided an S-spring assembly 24, at thisend of the housing. This assembly comprises a pair of S springs 25disposed on opposite sides of a ring member 26. A hub element 27, having1 the tapered support 14, as previously described, holds one enlargedend portion of a torsion bar and is disposed in the S-spring assembly, apin eccentric 28 and lock 29 being provided as indicated. Within thering member 26 an annular pressure compensator 30 is disposed. An ringor gasket 31, a housing-cap 32, and name plate 33 are secured, in theorder named, at this end of the housing.

The special S-spring assembly, above described, permits the movableparts of the assembly to be relatively free for longitudinal movementwith respect to the housing, while remaining rigidly fixed fortransverse forces. Among its other advantages, this arrangement, asabove pointed out, compensates for strains caused by diiferent rates ofexpansion of the parts within the gyro relative to the housing.

The housing may be filled with the liquid through a plug 34 in the plate33. Under temperature cycling the diiferent rates of expansion of theliquid and the housing are compensated for by the annular member 22 asdescribed above.

Also, the gimbal being immersed in the fluid is given a partiallybuoyant support which has the etfect of reducing its sensitivity tolinear acceleration and shock.

It will be seen that the pick-off here provided is hasically adifierential transformer. The mutual inductance between the primary andsecondary of this transformer is varied with the relative angularposition of the laminations on the rotor 11. This in turn is efiYectedby the rotation of the gimbal about the output shaft. Thus, thismovement is translated into an electrical signal which is proportionalto an input angular velocity.

While there has been shown and described a particular embodiment of thepresent invention, it will be apparent to those skilled in the art thatvarious changes and modifications may be made without departing from thespirit of the invention, and it is therefor intended in the appendedclaims to cover all such changes and modifications as fall fairly withinthe spirit and scope of this invention. i

What is claimed is:

1. A gyroscope comprising a gimbal; a rotor pivotally supported withinsaid gimbal for rotation about its axis of spin; a housing for saidgimbal pivotally supporting it to permit its movement aboutan axisperpendicular to said axis of spin; oil carried within said housingsurrounding said gimbal for damping the movement thereof; an annularmember secured to said gimbal and adapted to expand so as to decreasethe space between said member and housing with increases in temperaturethereby minimizing variations in the damping factor of said oil.

2. A gyroscope comprising a gimbal; a rotor pivotally supported withinsaid gimbal for rotation about its axis of spin; a housing for saidgimbal, pivotally supporting it to permit its movement about an axisperpendicular to said axis of spin; a viscous liquid within said housingsurrounding said gimbal for damping said movement of said gimbal; and abody of matter disposed between said gimbal and said housing, andadapted to expand with increases in temperature into locking engagementwith said housing to lock said gimbal against further rotation when saidbody reaches a predetermined temperature.

3. A gyroscope comprising a gimbal; a rotor pivotally supported withinsaid gimbal for rotation about its axis of spin; a housing for saidgimbal pivotally supporting it to permit its movement about an axisperpendicular to said axis of spin; oil carried within said housingsurrounding said gimbal for damping said movement of said gimbal; nylonring secured to said gimbal for rotation therewith within said housingand adapted to expand thereby to decrease the space between said ringand housing with increases in temperature, thereby minimizing resultantvariations in the damping factor of said oil.

4. A gyroscope comprising a gimbal; a rotor pivotally supported withinsaid gimbal for rotation about its axis of spin; a housing for saidgimbal, pivotally supporting it to permit its movement about an axisperpendicular to said axis of spin; a viscous liquid within said housingsurrounding said gimbal for damping the movement of said gimbal; and abody of matter secured to said gimbal and disposed between said gimbaland housing, said body having a greater coefficient of expansion withtemperature increases than said housing for decreasing the space betweensaid body and housing with increases in temperature, thereby minimizingvariations in the damping factor of said fluid.

5. A gyroscope comprising: a gimbal; a housing for said gimbal pivotallysupporting it for motion about an axis; a viscous liquid within saidhousing surrounding said gimbal for damping said motion; and a plasticannular member disposed between said gimbal and said housing fordecreasing the space between said body and said housing with increasesin temperature, thereby minimizing the effects of variations in theviscosity of said liquid.

6. A gyroscope comprising: a gimbal; a housing for said gimbal pivotallysupporting it for motion about an axis; a viscous liquid within saidhousing surrounding said gimbal for damping said motion; and an annularnylon ring secured to said gimbal for movement therewith within saidhousing for decreasing the space between said ring and said housing withincreases in temperature, thereby minimizing the effects of variationsin the viscosity of said liquid.

7. An inertial guidance instrument, comprising: a mass member; a housingfor said mass member pivotally supporting it for motion about an axis; aviscous fluid within said housing surrounding said member for dampingsaid motion; and an expansible, plastic annular member disposed betweensaid mass member and said housing for decreasing the space between saidplastic member and said housing with increases in temperature, therebyminimizing the efiects of variations in the viscosity of said fluid.

8. An inertial guidance instrument, comprising: a mass member, a housingfor said mass member pivotally supporting it for motion about an axis; aviscous fluid within said housing surrounding said member for dampmassmember when said body reaches a predetermined temperature.

9. An inertial guidance instrument, comprising: a mass member, a housingfor said mass member pivotally supporting it for motion about an axis; aviscous fluid within said housing surrounding said member for dampingsaid motion; and an expansible, annular, nylon ring member disposedbetween said mass member and said housing for movement with said massmember within said housing for decreasing the space between said ringmember and said housing with increases in temperature, therebyminimizing the effects of variations in the viscosity of said fluid.

10. An inertial guidance instrument, comprising: a mass member, ahousing for said mass member pivotally supporting it for motion about anaxis; a viscous fluid within said housing surrounding said member fordamping said motion; and an expansible, annular nylon ring memberdisposed between said mass member and said housing adapted to expandwith increases in temperature into locking engagement with said housingto preclude further movement of said mass member when said body reachesa predetermined temperature.

References Cited in the file of this patent or the origmal patent UNITEDSTATES PATENTS

